The histochemical and biochemical determination of carbonic anhydrase activity in isolated cells of the gastric mucosa will be studied. Antibodies to carbonic anhydrase will be raised and the immunolocalization of this enzyme in the gastric mucosal cells will be investigated. Attempts will be made to determine the hydrogen ion content and chloride concentration of internalized canaliculi in isolated parietal cells with micro ion specific electrodes. Receptor sites on isolated cells will be localized with radioactive hormones and secretagogues to determine their distribution and fate. The mechanism and control of gastric mucus secretion will be investigated in the isolated cells.